Electrical signaling system



J. F. MACKENZIE ELECTRICAL S IGNALING SYSTEM May 9, 1944.

Filed Oct. 2, 1940 STATION 3 STATIO 2 MECHANICAL LATC Hl NG RLY.

SIREN INVENTOR. JOHN FRANCIS MACKENZIE BY ATTORNEY c STATION WC 1 SYNCHRONOUS MOTOR TIMING CONTROL MOTOR.

Patented May 9, 1944 ELECTRICAL SIGNALING SYSTEM John Francis Mackenzie, Liverpool, England, as-

signor, by mesne assignments, to Automatic Electric Laboratories, Inc., Chicago, 111., a corporation of Delaware Application October 2, 1940, Serial No. 359,414 'In Great Britain October 3, 1939 '7 Claims. (01. 177-352) i V The present invention relates to electrical signaling systems and is more particularly concerned with systems suitable for the control of air raid warning signals and the like. With the arrangements generally adopted whereby an air raid warning is given by electrically-operated sirens giving a wailing note While the cancellation of the warning is given by the sirens sounding a steady note, it has been found that where a plurality of sirens are provided in different parts of a given area, confusion between the two signals is likely to occur unless all the sirens wail in syncronism.

One method of meeting this requirement is by the use of pilot wires interconnecting the various. sirens whereby either the current supplied to all the sirens concerned isinterrupted at one point or relays located at the various points are operated in synchronism to give the necessary control. This, however, is a very costly expedient as the expense of the pilot wires may be considerable and to this must be added the cost of the relays if the pilot wires are not to be of 'very heavy gauge. The chief object of the present invention is to provide a solution of the problem in question which is very much cheaper and can be achieved by the addition of only a small amount of equipment of a type already in general use. l

According to the invention in an electrical signaling system for effecting the synchronous operation of a plurality of electrically controlled sound generators producing coded audible signals and located at different points the contacts associated with the difierent sound generators for pro ducing the coded operation are arranged to be operated by synchronous motors fed from a common controlled frequency supply.

Conveniently the actual setting of the sirens into operation is efiected in response to high fre I quency signals superimposed on the supply mains in a manner which is now well'understood and has secured a large measure of adoption and in thiscase the use of pilot wires is not necessary at all.

The invention will be better understood from the following description of one method of carry ing it into eifect which should be taken in con junction with the accompanying drawing. The figure discloses three sirenstations; like apparatus isemployed at all of them, and accordingly only one has been shown in detail. d

It is important that thepowe'r supply should be common to all the siren stations concerned and preferably it 'will comprise controlled fre: quency alternating current mains which are'now commonly available over a wide area. The conductors L and N together comprise one such main in a network of mains connected to the common source AC. Alternatively use might be made of a controlled frequency ripple on a direct current supply. .The synchronous motor is represented by WC and produces suitable periodic operation of the contacts WCA, for instance six seconds closed and three seconds open. The contacts of thevarious motors WC are synchronised beforehand so that they open and close together and this synchronising operation will probably involve avisit to the various control points at a time when a periodic check signal is being applied to the system.

When it is desired: to soundthe sirens to give an alarm, a characteristic signalis applied to the network to eifect the operation of a responding unit which closes contacts one, for instance in the manner described in British Patent No. 518, 877, accepted March 11, 1940. Thereupon relay RW is operated and this is provided with a mechanical locking action so that contacts rw are closed and remain closed after the signal ceases. If, at the instant contacts ijw close, contacts WCA are already. closed, a circuit 7 is completed for starting up the motor TC; if not, the motor will be started when contacts WCA next close. This thereupon operates the cam contacts TCB whereby the motor circuit is maintained for a period of two minutes represented by one revolutionof the cam shaft. Contacts TCC are also closed and complete the circuit for the siren S. Th'is therefore operates togive thewailing warning signal under thecontrol of contacts WCA and all the other sirens on the system will operate at the same time since the various contacts WCA are synfihronised. It will be understood that if the operating times of the responding devices are slightly difierent, one siren may get in an additional Wail; compared with the others but this will not cause any confusion Similarly no difiiculty would arise if the varioussirens were separately controlled 'by hand forinstance in response to telephonic instructions and wer thus not all connected up together. 'At the end of the twominute period, contacts TC A are closed to com{ plete a resetting circuit by Way of the righthand coil of relay RW so' that contacts rw are opened and at about the same time contacts TCB are opened to interrupt the maintaining circuit for the motor TC." Contacts TCC arealso restored at this time so that the initial circuit of the motor TC is connected up in readiness for a further operation;

When the fall clear signal i'sto be given, a different superimposed signal is transmitted which has the effect of operating contacts grc. Thereupon relay RC operates and contacts T0 are therefore closed and remain so. The motor TC is therefore again started up and at contacts TCC the circuit for the siren S is completed but since in this case the contacts WCA are excluded, the siren is sounded steadily for two minutes. At the end of this period relay RC is reset over its righthand winding and the equipment is thus restored to normal.

It-will thus be appreciated that by making use of synchronou motors kept in step by feeding from controlled frequency supply mains, it is possible to secure synchronisation of a group of warning sirens in an area in a .very simple and inexpensive manner.

I claim:

1. In a signaling system, a plurality of stations, an impulse generator at each station, an alternating current network serving said stations, synchronous motors at the "stations operating over said alternating current network and driving said generators in synchronism, devices at the different stations operated substantially simultaneously and each effective when operated to cause the generator at its station to begin to generate impulses, said impulses being generated in unison by the generators at the different stations, a second motor at each of said stations, means at each station for transmitting the first impulse gener ated thereat to saidsecond motor at that station to initiate its operation, means at each station controlled by said second motor for thereafter sustaining its operation independentl of said generator for a predetermined "interval, a responding device at each station, an means at each station controlled by said second motor thereat during said interval for transmitting the impulses generated by the generator at that station to the responding device at that station.

2. In a signaling system as claimed in claim 1, means at each station controlled by said second motor thereat to operate said device at that station at the end of said interval thereby to cause the generator at that station to stop generating impulses.

3. In a signaling system, a plurality of circuits, a normally open switch in each of said circuits, means for closing all of said switches substantially simultaneously thereby to cause current to begin to flow over all of said circuits'at substantially the same time, synchronized interrupters in said circuits operated continuously and effective to repeatedly interrupt all of said circuits in unison, a motor connected to each circuit and started to operate by the current all of said contacts substantially simultaneously thereby to start all of said motors over their respective circuits, means individual to each motor and controlled by that motor, when started, to sustain the operation of said motor independently of the circuit over which it was started for a predetermined interval, and other means individual to each motor and controlled by that motor, when started, to disconnect said circuit from said motor and connect it to the responding device at that station for the duration of said interval.

5-. In combination, two circuits, a normally open switch in each of said circuits, means for closflowing over that circuit following said closure of the switch in said circuit, a plurality of responding devices each corresponding to a different one of said motors, means individual-to each motor and controlled by that motor, when started, to disconnect from said motor the circuit over which said motor was started and to connect said circuit to the responding device corresponding to that motor, and means for maintaining all of'said motors in operation for a predetermined interval of 'time,independently of their respective starting circuits."

' 4'. In a signaling system, a pluralityof stations, a responding device at each of said stations, a motor at each of said stations, 'a circuit at each station normally connected to the motor at that station, a contact in each of said circuits normally maintaining that circuit open, means for closing ing eitherof said switches at will, thereby to cause r 'current't'o flow over either circuit, a continuously operated interrupter in one of said circuits efiective to repeatedly interrupt the flow of current over that circuit when the switch in said circuit is closed, a motor normally connected to said circuits and effective to begin a cycle of operation responsive to the receipt of current over either of said circuits --following closure of the switch in that circuit, a responding device, means controlled by said motor after a cycle of operation has been begun to disconnect said circuits from said motor and connect them to said device, said last means efiective to maintain said circuits connected to said device for the remainder of said cycle and then to reconnect them to said motor, said device operating interruptedly during said remainder of the cycle if it receives current over said one circuit and operating continuously during said remainder'of 'the cycle if it receives current over said other circuit, and means efiective to sustain the operation of said motor for the remainder of said cycle after said circuits have been disconnected from said motor.

6. In combination, a motor, a responding device, a relay'of the type adapted to operate when momentarily energized and to remain operated until again momentarily energized, means for momentarily energizing said relay to operate same,'a normally open contact on said relay effective to close a circuit to said motor upon said operation of the relay, thereby tostart said motor, means controlled'by said motor, when thus started, to close another circuit for said motor to maintain'it'in operation for a predetermined interval and, at substantially the same time, to discon- 'nect said first circuit from said motor, said last means efiective to connect said first circuit to said responding device for the duration of said interval and,'at the end of said interval, to reconnect said first circuit to said motor and 'diS connect said second'circuit from said motor, and other means controlled bysaid motorat the end ofsaid interval to again momentarily energize said relay to restore said contactto normal.

'7. In" combination, a normally open circuit, means operated to close said circuit, a motor normally connected to said circuit and'responsive to c JOHN FRANCIS MACKENZIE. I 

